The massive forward deployment of Soviet forces in Eastern Europe is a dominant feature of the postwar political order. It provides the basis for Soviet political control over Eastern Europe and constitutes the Soviets' only concrete leverage over Western Europe. Starting in the early 1950s—in the aftermath of the Berlin crisis and the Korean War—this situation both led the West to direct the reconstruction of Western Europe and encouraged an evolution in U.S.-West European ties based in considerable measure on a military relationship: that is, on extended deterrence reinforced by U.S. forward-force deployments.